Machine tools are widely used to form sheet metal and other workpieces into various configurations using cooperating upper and lower tools. In some cases, an upper tool mounted in a tool holder of the machine tool is moved downwardly against a workpiece disposed on a die, which cooperates with the upper tool. Some dies have resiliently moveable portions that facilitate forming the workpiece about contours of the tools. Tooling of this nature may deform the workpiece by simply providing a contour, in which case the cooperating surfaces of the tools will generally have radiused edges. Other tooling cuts through the workpiece. Such tools typically have sharp cooperating edges to shear the workpiece. Some tooling provides both forming and cutting action, for example, by having forming edges about a portion of the periphery and cutting edges about the remainder of the periphery.
Generally, machine tools have a limitation as to the maximum size (e.g., the maximum diameter) of the tools that can be used. If the diameter of a conventional forming tool is smaller than the length of the desired form, then multiple operations may be required to create the full length of the form. This is inefficient and costly and it may require using multiple tools (or even multiple machine tools) to obtain the desired form.
Some expandable form tools have been devised to make forms having a length greater than the diameter of the tool's main body. However, the expandability of those tools causes some inherent weakness.
It would be desirable to provide a forming tool that can create a form larger than the normal diameter of a conventional forming tool, e.g., such that a large form can be produced in a single stroke. It would be particularly desirable to provide a forming tool of this nature that is durable in terms of withstanding breakage over long periods of rigorous use.